LASIK fixes three common vision problems: nearsightedness (myopia), farsightedness (hyperopia), and astigmatism. All three are caused by the shape of your cornea bending light incorrectly, and LASIK works by permanently reshaping that cornea so light focuses precisely on your retina. About 90 to 95% of patients end up with 20/20 vision or better, and 99.5% achieve at least 20/40, which is the legal threshold for driving without glasses in most states.
Nearsightedness, Farsightedness, and Astigmatism
These three conditions are called refractive errors, and they all come down to the same basic problem: the curve of your cornea doesn’t match the length of your eye, so light lands in the wrong spot. In nearsightedness, distant objects look blurry because light focuses in front of the retina. In farsightedness, close objects blur because light focuses behind it. Astigmatism means the cornea is shaped more like a football than a basketball, scattering light in multiple directions and making everything slightly distorted at any distance.
LASIK can correct nearsightedness up to about -12.0 diopters, farsightedness up to +6.0 diopters, and astigmatism up to 6.0 diopters. If your prescription falls within those ranges, you’re likely in the treatable zone. Prescriptions beyond those limits may require a different procedure.
How Corneal Reshaping Works
Your cornea is the clear dome at the front of your eye, and it does most of the work bending light toward your retina. During LASIK, a surgeon first creates a thin flap on the surface of the cornea, then lifts it to expose the tissue underneath. An ultraviolet laser removes microscopic amounts of that tissue through a process called photoablative decomposition, which breaks chemical bonds without generating heat or damaging surrounding cells. The whole reshaping takes less than a minute per eye.
For nearsightedness, the laser flattens the center of the cornea so light bends less steeply. For farsightedness, it steepens the center by removing tissue from the edges. For astigmatism, it smooths out the irregular curvature so the cornea becomes more uniformly round. Once the flap is laid back down, it reattaches naturally without stitches.
Most modern clinics use a femtosecond laser to create the flap rather than a mechanical blade. The laser-created flap is significantly more uniform in thickness and allows for more precise repositioning afterward. In one study, flaps made with the femtosecond laser varied by only about 6 microns from the target thickness, compared to about 21 microns of variation with a mechanical blade.
What LASIK Cannot Fix
The most common misconception is that LASIK eliminates the need for reading glasses as you age. It doesn’t. The age-related loss of close-up focus, called presbyopia, happens because the lens inside your eye gradually stiffens and can no longer change shape to focus on nearby objects. Since LASIK reshapes the cornea and doesn’t touch the internal lens, it can’t restore that flexibility. Most people start noticing presbyopia in their early to mid-40s, and it progresses regardless of whether you’ve had LASIK.
There is a workaround called monovision, where the surgeon intentionally corrects one eye for distance and the other for reading. Your brain learns to favor whichever eye has the sharper image for the task at hand. It works well for many people, but some find it uncomfortable. Depth perception can feel slightly off, particularly while driving or playing sports. A trial with contact lenses before surgery is the best way to test whether monovision suits you.
LASIK also doesn’t treat eye conditions like cataracts, glaucoma, or diseases of the retina. It’s specifically a solution for refractive errors caused by corneal shape.
Who Qualifies for LASIK
Your prescription is only one part of the equation. Surgeons also evaluate corneal thickness, because the laser needs enough tissue to reshape without leaving the cornea dangerously thin. A common guideline is maintaining at least 275 microns of remaining corneal tissue after the procedure, though there’s no universally agreed-upon minimum. Thinner corneas may still qualify with careful planning and thinner flap creation.
Your prescription also needs to be stable. If your glasses or contact lens prescription has changed significantly in the past year, most surgeons will ask you to wait. Patients under 18 are generally excluded for this reason, as their eyes are still developing.
Several health conditions can disqualify you. Uncontrolled autoimmune diseases, uncontrolled diabetes, severe dry eye that doesn’t respond to treatment, and active eye infections are all contraindications. Pregnancy and breastfeeding temporarily disqualify you because hormonal changes can shift your prescription. Certain medications, including isotretinoin (used for acne) and amiodarone (a heart rhythm drug), also rule out the procedure while you’re taking them.
Modern LASIK Precision
Today’s procedures are more precise than what was available even a decade ago. Topography-guided LASIK, which maps the unique surface contours of your cornea and customizes the laser pattern accordingly, produces notably sharper results than the older wavefront-optimized approach. In a clinical comparison, 57% of eyes treated with topography-guided LASIK achieved 20/16 vision or better (sharper than “perfect” 20/20), compared to 17% with the standard method. Nearly half of patients in the topography-guided group could see better without glasses after surgery than they could with glasses before it.
Recovery and Stabilization
Most people notice dramatically clearer vision within hours of surgery, though the first two to four hours involve stinging, burning, and blurriness as the corneal flap begins healing. By the next day, the majority of patients can drive and return to most daily activities. Your vision will continue to sharpen and fluctuate over the following weeks as the cornea settles into its new shape. Full stabilization typically takes three to six months, during which your prescription may shift slightly before locking in.
Dry eyes are the most common side effect in the weeks following surgery and usually resolve on their own. Halos or glare around lights at night can occur early in recovery and tend to diminish as healing progresses. Enhancement procedures, essentially a second round of laser correction, are occasionally needed if the initial result under- or overcorrects.